Galvanometer



M arch 7, 19349.. F. M, KANNENSTINE 2,149,442

GALVANOMETER Filed June 11,4937 3 sheets-sheet 2 indica/whoa M'.KANNENSTINE E40. @mw

Gum/Maf Mach 7, 1939.l I F. M. KANNENSTINE f 2,149,442

GALVANOMETER Filed June l1, 1937 3 Sheets-Sheet 3 Patented Mar. 7, 1939.UNITED 'STAT-Es' GALVANOMETER.

Fabian M. Kannenstine, HoustomTex. Application 'June 11, 1937, SerialNo. 147,642

5 Claims. 'I'he invention relates to oscillo'graphs and moreparticularly to the current responsive elelis ment thereof whichcomprises the reflection type of galvanometer having a movable loopwhich oscillates inaccordance with the amplitude and frequency of a owof current.

. It is an object -of the invention to provide a 'current responsiveinstrument having relatively small transverse dimensions whereby aplurality may be in juxtaposed position and occupy a minimum of space. y

It is also an object to provide an oscillograph having a plurality ofcurrent responsive galE vanometers`of a relatively small transversedimension whereby a plurality of such instruments may be used injuxtaposed relation without producing a desensitizing effect of one uponthe other.

A further object is to` provide a current responsive instrument of thereflection type in which light from the mirror mounted upon the movingsystem is reec'ted substantially at right angles to the transversedimension and to the magnetic lines of force through the air gap.

A further object is to provide a. reflection type of' instrument havinga removable suspension system which is immersed in a damping fluidcontained within a chamber including the air gap of the magneticcircuit.

A more specic object is to provide an in'- strument of the reflectingtype having a housing in the magnet to receive the suspension system ofthe instrument.

A further speciiic object is to .provide a reiiection type of current'responsive instrument having ya housing within' the magnet in which inserts of high permeability are embedded whereby a small/air gap isobtained and thereis a high iiux density through the moving system. v

Still another object is to vprovide a current responsive instrumentwhich adapts itself to emcient use in groups to record a plurality ofwave traces in closely juxtaposed relation on a single recording stripas is "desired, for example, in

recording impulses in theseismic method oi geophysical prospecting.

Other and further objects-.will be apparent from the followingdescription taken in connection with the drawings in which:

Fig. 1 is a sectional view of a gaivanometer embodying the invention.

Flg..2 is a front elevation taken'from the right of Fig.- `1 and-showigparts-in section.

Fig. 3 is a'section'al view-on line I-i of Fig. 1.

(Cl. P11-95) the'construction of the upper and lower ends, respectively,of the moving coil. l

Fig. 6 an elevational view of the stem for supporting the moving system.

Fig. 7 is similar to Fig. 6 but taken at right angles thereto.

Figs. 8 to 13 are sectional v iews of the stem shown in Figs. 6 and 7and taken respectively on lines 84 to I3-I3 of those figures.

, Figs. 14 and 15 are views illustrating a modiiied form of theinvention.

Fig. 16 is a plan View partly in section of an oscillograph systemconstructed in. accordance Fig. -17 is a side elevation taken on lineI'l-I'I o f Fig. 16.

with the invention.

An instrument involving the invention is illustrated in Figs. 16 and 17in which an oscillograph cabinet IIIl encloses a recording strip I I I,a light source I I2, and a galvanometer generally designated as II3, andcomprising a plurality of current responsive elements or galvanometers IIl which will be more fully described. The galvanometer Ill isadjustably and removably se cured in a mounting block II5 by set screwsII6'. As already indicated, and as will be more fully described, thegalvanometer Ill is of the reection type inv which a mirror is mountedupon the moving system and a beam of lightl I I8 is directed upon themirror 98 for reflection upon a screen or a recording tape III', wherebythe movements of the mirror may be observed or re corded. Current isconducted to terminals 26 and 35 of galvanometer III through Vconductors|20 and I2I, respectively, whereby an actuating current is conductedthrough the instrument.

With the assembly just describedl it is understood that a beam of lightIIB 'falls upon the moving mirror 98 within the galvanometer IIl and isreiiected at I-I9 uponthe recording strip III to produce a record of thefrequency and amplitude of 'the currents through the gal- Theconstruction and operation of the galvanometers III of the galvanometerbank IIS are best `illustrated in Figs. v1 to 15. Each of theseinstruments comprises essentially aj'magnet I, a housing 2, and asuspensionsystem generally designated as 3. v

` Magnet I may comprise an electromagnet as illustrated in theembodiment' shown in Figs. 14y

. and 15, or preferably, may be a permanent magnetof the horse shoe typeas illustrated in Fig. 1.

In either event the magnet comprises spaced poles I and 5, each having acentral bore 8 to receive screws l for a purpose that will be madeapparent. l

The housing 2 is made up of non-magnetic material, preferably metal, andhas the same transverse dimension as does magnet I. Downwardly extendingportion IB of this housing has a tubular bore II to receive the lowerend of the suspension element hereafter described. The upper portion ofthe housing provides a mounting surface l5 for the suspension assemblyand has an elongated cavity I6 which'is an enlargementfof bore II tolikewise receive parts of the suspension element..

An important feature of the invention is the provision of tapered slotsI1, see Fig. 3, in the walls of the housing 2 adjacent poles Il and 5 ofthe magnet. Positioned within these slots are high permeability insertsI8 which are xed to the housing as by soldering. `These inserts aredrilled and tapped to receive the threaded ends of machine screws 1, andin this manner the surfaces of the inserts I8 and poles 6 and 5 arebrought into intimate relation and the magnet andhousing are formed intoa composite unit.

In the front wall of the housing 2 above pole piece 5 is provided anopening 20 having a shoulder 2l against which is positioned a Window 22,which may have a condensing lens as illustrated, and which is xed withinthe opening asby a suitable cement. This window serves to admit light tothe mirror of the moving system and also to permit the reiiected lightto pass outwardly from the housing.' At the same time the window 22serves as a fluid tight closure to re` tain a damping -fluid within thehousing. Above window 22 is a flange 25 on housing 2. A drilled bore inthis flange receives binding post 26 which serves as one terminal on theinstrument.

The suspension system includesA a stem whichv comprises a tubular bodyportion .30 which extends downwardly Within vbore vI I- in housing' 2.

Flange 3l extends outwardly from the stem body 3B and iscarefullymachlned to nt upon surface I5 of housing 2.V Machine screws 32secure the stem and housing in fixed relation. If desired a gasket maybe used between flange 8| and housing 2 to insure a liquid tight sealbetween the housing and stem. n A

Binding post 3E passes through an insulating bushing 36' in an openingin ange 3| and is secured in place by 'means of a nut 31 -and a t washer38. The end of the binding post 35 ex-A tends downwardly within cavityI6 to provide a connection with a wire 4I) from the vibrating ele mentwhereby binding post 36 serves as the other terminal of the instrument.

An upper suspension Vsupport SI comprises a cylindrical stem 42`and adownwardly tapering end portion 43 which nts within a tapered opening ina boss 4t eideluding upwardly from ange 3|. Washers 45 and 46 and aninterposed spring 41 are placed uponstem 62, the spring being held intension by means ofcap 48 which is threadably attached to boss. 44. Asthe tapered end 63 of the support presents a shoulder against'` whichthe washer 45 is urged by spring 61, close. sealing engagement ismaintained between the suspension support and the stem. In order toprovide for rotation of support member 4I to adjust the instrument acollar-50 and sternl 42 are drilledl for a press fit with pin 5I. Thisconstruction holds the parts in assembled relation and obviously the pin5I. may be used as a handle lfor rotational adjustment of the suspensionsupi port 6I.k A projection 52 on the lower end of aisance thesuspension support is adapted to have a suspension ribbon SI1-solderedthereto.

The construction of the stem 30 is such that the galvanometer element,which comprises the luctance of the magnetic circuit the opposite sidesof the stem 30 are provided with tapered recesses at 60 (see Fig. 8),and high permeability inserts BI are fixed therein, preferably by meansof hard solder. A slot 62 extends transversely of the stem 30 throughoutthe extent of inserts 6I, the inner faces 64 of the inserts being'co-planar with the walls of the slot. y A .In a similar manner outersurfaces 63 of 'inserts 6I coincide with the cylindrical outer surfaceof stem 30.

At the upper end of slot 62 a bushed opening passes diagonally upwardthrough stem 30 to provide a passageway for. conductor 40, which iselectrically connected to binding post 35 and toV an anchor pin 68.

' Below inserts 6I slot 62, extends but partially through stem 30;leaving a ledge 65 which is drilled at 66 to receive an insulatingbushing 61 through which the anchor pin 68 passes. This pin is providedwith a shoulder near its upper end to iix the position of the pin withinbushing 61. Within slot 62 below anchor pin 68 is a tensioningarm 10pivoted on a pin in opening 1I which extends transversely of the slotThe pivoted end of arm 10 is bifurcated and 'has rotatablymountedtherein and upon pin 12, an ivory roller 13 about which the lowersuspension ribbon is adapted to pass.. The end of arm 10 opposite vthepivot vpin in opening 1I is attached to a tenlower end of slot 62.-

By means of this construction it is obvious that arm 10 may beresiliently and adjustably urged downwardly to place tension upon thesuspension system hereinafter described.

Above inserts 6I the stem y30 is channeled at right'angles to slot 82 asis best illustrated in Figs. 7 and I1l to 13. Alongitudinal groove 80 ofsumcient depth to permit axial suspension of the galvanometer elementhas flared outer walls 8| and terminates at its lower end in acylindrical bore 82. This construction enhances accessibility totheupper end ofthe suspension system, bore 82 also serving as the chamberwithin which the galvanometer mirror is positioned adjacent window 22.Slot 62 and groove ,80 are in longitudinally spaced relation and asquare axial bore therebetween is shown at 83. A

The galvanometer element comprises upper and lower'ribbon suspensions 90and 9| connected'to galvanometer coil 92 shown in detail in Figs. 4 and5. This elongated coil comprises a plurality of turns of insulated' wireand is suspended in closely spaced relation with walls of the axial boreof stem 30. One end of thevwire forming Ycoil 52 terminates at thelowerend of the coil that mirror 98 is within bore 82 adjacent window 22.Lower suspension ribbon 9| is then passedv beneath roller. "I3, the endthereof being brought,

r upwardly and soldered to anchor pin 68. A cirto complete thegalvanometer suspension. By

means of this construction it is apparent that the reflecting surface ofmirror is -at right angles to the magnetic iiuxin the air gap and issensibly parallel to the longitudinal axis of the coil. l

lSuspension ribbon 90 is soldered to projection 52 on suspension support4| in sucha manner cuit is thus completed from binding post 26 andsuspension support 4l to and through the vibrating element to anchor pin61, which, as above described, is electrically connected to binding post35 through insulated wire 40.

Tension is applied to the vibrating system by means of adjustment ofscrew 15in spring 14,'

while proper angular orientation of the coil relative to the magneticlines o f force within the air gap is effected by means of pin 5I andsuspension support II.

Before installation ofthe suspension 'assembly l in housing 2 a suitablefluid, as for example a suitable mineral oil, is poured into the chamberin the housing to serve as a damping agent for the vibrating system tosubstantially eliminate the natural period thereof: The modificationillustrated in Figs. 14 and 15 comprises end plates Illand Ill, joinedby core |02 to form a spool'for coil Ill whereby an 'electromagnet isformed. End plates I and |0| are provided with flanged pole pieces toprovide an elongated air gap III in which a plurality of galvanometerelements are supported within a housingV generally designated as IIII.'Ihe construction of this embodiment is otherwise in accordance with thegeneral details as above set forth in connection with the embodimentillustrated in'ligs. l'to 13. The operation of the above describeddevice is believed obvious. Electrical impulses of which a wave trace isto be recorded are conducted to the instrument through conductors |20and I2I connected to terminals 2i and l5 of the galvanometer I Il.Current thus ilows from terminal 35 through conductor 4l to support Il,thence through the suspension system, comprising ribbon suspensions sl,Il and coil 92, totheinstrument frame and the terminal 2l. Currentthrough the coil I2 causes the coll to be deiiected from its normalposition by an amount depending upon the strength ofthe current.Since'this current is varying, the coil l2 and its associated mirror Itoscillate in response to the strength `and frequency of the yactuatingcurrent. The ray of light III from the lamp H2 passes throughwindowlltomirror andis'reiiectedat Illto4 sensitized recording-tape IIIto produce a trace which represents the frequency and amplitude of theinitiating impulses. It is understood that they operation as abovedescribed applies to each of the galvanometers of the galvanometer bankIII I7| andthatthegalvanometersaresoadjustedthat together by a bindingthread a plurality of wavetracesare lrecorded upon sensitIzed tape I Iin paralielrelation.

From the foregoing itlwill be apparent that the invention provides anoscillograph which includes a galvanometer having a small transversedimension whereby s. plurality of such galvanometers may be arranged inside by side relationship to -form a compact and' eilicient galvanometerbank. At thejsame time the galvanometer is so constructed thatsthemirror on the suspension system is positioned above thepole pieces ofthe magnet andatfor substantially at, right angles to both theminimumdimension of; the instru-v ment and the magnetic lines of force in theair gap whereby the necessity of providing openings in the pole piecesto accommodate the passage of the light beam is obviated. l

While the preferred embodiment of the inven- 1. A current'responsiveinstrument comprising a substantially U-shaped magnet having spaced polepieces, a housing positioned between said .pole pieces, magnetic insertsembedded in the opposite walls of the housing adjacent said pole piecesto form an air gap-in the piane of the magnet. a galvanometer elementsuspended between said inserts and ,within said housing, and meansoutside the air gap and movable with said galvanometer element forindicating dispiacement of the element withinsaid magnetic field.

2. A current responsive instrument comprising meansfor producing amagnetic eld, said means having an air gap .in the magnetic paththereof,

meansfforming'a hollowvchamber including said I air gap. a galvanometerelement suspended in said chamber, and means mounted on thegalof theelement within said magnetic field.

3. A current responsive instrument comprising a magnet having spacedpole pieces, a non-magnetic housing about the pole pieces and formingtherewitha iluid chamber, anda galvanometer element suspended-in-saidchamber, said element having mounted thereon outside the air gap avertically disposed mirror having its'reecting surface substantiallyperpendicular to the mag- .netic flux between said pole pieces.

. A4. In an oscillograph, a galvanometer assembly comprising anelongated stem having an axial 5. A current responsive instrumentcomprising I a -substantially' u-shaped magnet. a non-magn etic -housingwithin the magnet and extending outwardly beyond the poles thereof, awindow in the housing adjacent the end ofthe magnet and transversely ofthe flux between the magnet poles. s stem sudsbxe within said naming andro- .element therein, and a mirror on said element adapted to cover thehousing'and enclose a damping iiuid therein, said stem having agalvanometer adiacent the window to reiiect light in the direction o!the magnetic iiux.

rameurs.

vanometel'felement outside the air gap and mov- 4foable with` theelement for indicating displacement

